1. Field of the Invention
The present invention relates to an impact tool, such as an impact driver, which causes an anvil protruding from a front side of a housing to generate a rotary impact force.
2. Description of Related Art
As disclosed in Japanese Laid-open Patent Publication No. 2003-231067, an impact tool such as an impact driver includes: a spindle disposed in a housing and configured to be rotated by a motor; an anvil disposed in front of the spindle and rotatably supported by the housing through a metal bearing in a manner coaxial with the spindle, a front end of the anvil having an insertion hole for attaching a bit and protruding from a front side of the housing; and an impact mechanism configured to transmit a rotation of the spindle as a rotary impact force to the anvil, and an action of the impact mechanism caused by a rotation of the spindle is transmitted to the anvil as a rotary impact force.
A bearing hole is formed at the rear end of the center axis of the anvil, and the front end of the spindle is rotatably supported in the bearing hole. Further, a connecting opening radially extends in the anvil and connects the bearing hole and the inner peripheral surface of a metal bearing to provide a communication therebetween. Grease in the bearing hole is supplied to the inner peripheral surface of the metal bearing through the connecting opening so that lubrication is ensured between the anvil and the metal bearing.
However, the connecting opening is formed in such a position to correspond to a grease receiving groove that is circumferentially formed on the inner peripheral surface of the metal bearing and at a center of the metal bearing in the axial direction thereof. For this reason, the connecting opening is often formed in the anvil in a position ahead of the bearing hole and is connected at the front end of the bearing hole. Since the insertion hole for a bit is formed in the anvil at a region ahead of the connecting opening, the overall length of the anvil is determined based on a depth of the insertion hole at the region ahead of the connecting opening. In consideration of the fact that a necessary depth for the insertion hole has to be ensured for the anvil, the size of the anvil cannot be reduced.
In view of the above drawback of the prior art, the present invention seeks to provide an impact tool, which can reduce the overall length of the anvil while ensuring necessary lubrication between the anvil and the metal bearing.
The present invention has been made in an attempt to eliminate the above disadvantages, and illustrative, non-limiting embodiments of the present invention overcome the above disadvantages and other disadvantages not described above. Also, the present invention is not required to overcome the disadvantages described above, and an illustrative, non-limiting embodiment of the present invention may not overcome any of the problems described above.